How much spark do I really need to ignite gas pilot?

I have attempted to repair an old heater in a building I own. It has a sophisticated contoller, and electrical ignition of pilot flame. The heater is worth saving, and expensive to replace. It really hasn't been used much.
To make a long story short, I have removed the pilot nozzle and igniter, to where I can plainly examine performance, while they are connected to the system. I have scraped and scratched at electrode surfaces, to minimize dielectric impediments to desired electrical arcing. There are sufficient low-radii at electrodes, to promote better sparking. The Johnson Controls G66AG-1 spark generator, which plainly says, "0.10 inch spark gap," cannot seem to reliably accomplish that length of spark. I detect some loss due to the spark cable, but not much.
I would have thought that an 0.05" spark would ignite the gas that comes out at the adjacent nozzle, but no! In disbelief, I lit the gas with a match, and it lit! But a consistent spark at a reduced gap, from 0.10" to 0.05" won't ignite the gas. It is very difficult for me to accomplish an 0.10" spark gap, else I'd know for sure that such a gap would reliably ignite the gas.
Will a bigger spark reliably ignite the gas? I'm flabbergasted that 0.05" spark won't do it. Could something else, like positioning, do it?
I've moved the electrode without any improvement. I've used a long screwdriver to cause the spark to occur at different places along the gas-jet; no real help. Nothing I've tried seems to work. Not surpringly, the spark will jump a greater distance, inside a flame, once a pilot flame already exists, but that's a little late to do any good!
Has anyone successfully repaired this problem before, by replacing the spark generator? How long a spark could I see with a new unit?
Over many years, I have often blamed the ignition coil, for automotive ignition problems. It has never proved to be the cause. So I hesistate to replace the spark generator. Can they deteriorate over the years?
Thanks, John
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John, There are 3 things that are needed for combustion. I'm sure that a plumbing business owner would know how to fix this type of problem for a building owner.
Jabs

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Being an old hot rodder, I'd say the longer the spark gap, the hotter the flame....

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